This invention relates to an optical instrument designed to analyze samples by means of narrow wavelength band light and more particularly to a system in which the narrow wavelength bands of light are generated by means of a spectrometer having a grating which oscillates at a high cyclical rate.
The general type of instrument of the present invention is disclosed in the Landa U.S. Pat. No. 4,264,205. As disclosed in this patent, an optical grating dispersing received light into a spectrum is oscillated at a high cyclical rate by conjugate cams. The conjugate cams not only achieve oscillation at a high cyclical rate, but also provide a rotation of the grating relative to the input drive axle to the cam mechanism that causes the grating to rotate through equal increments of wavelength for each equal angular increment of rotation of the input axle. Thus, by taking readings from the spectrometer at equal angular increments, readings from the sample are obtained at equal wavelength increments, for example, at two nanometer increments.
The above described instrument is an effective optical analyzing instrument, but it suffers from the disadvantage that the conjugate cams are an expensive mechanism and a long and relatively laborious procedure is required to properly adjust them when the instrument is being initially set up further adding to the cost of each instrument. In addition, there necessarily is some play or slop in the cam mechanism and, as a result, the measurements made by the instrument of the Landa patent are not precisely repeatable. This lack of repeatability becomes worse as the bearings in the mechanism began to wear with use of the instrument. In addition, the cam mechanism requires a large motor which adds substantially to the weight and size of the instrument. In addition, the cam mechanism generates a substantial amount of noise when the instrument is operating.